Submitted to: Crop Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 10/15/1996
Publication Date: N/A
Interpretive Summary: Warm-season, perennial grasses such as bermudagrass, are widely used for turf in tropical and subtropical regions throughout the world. Their use also extends into regions of transition between warm- and cool-season species. While substantial differences exist in the winterhardiness of turf bermudagrass cultivars, all are subject to freezing injury. Tolerance of turf bermudagrass cultivars to freezing is a major concern of turfgrass managers in regions subject to these climatic conditions. This study was undertaken to gain a better understanding of the genetics and physiology of tolerance to freezing stresses which will facilitate the development of new cultivars with cold tolerance. Bermudagrass plants were grown under cold acclimating and nonacclimating conditions. Proteins synthesized in the crowns of these plants were analyzed to determine if any differences could be detected for types or amounts produced. Several low molecular weight proteins were observed to be synthesized in response to the cold acclimating conditions. Specifically, one prominent protein, designated COR27, was isolated and the sequence of its amino acids was determined. Based on this analysis, COR27 was identified as a chitinase. This information gives some insight into the regulation of the cold acclimating process and may provide an opportunity for geneticists to improve the level of cold tolerance in bermudagrass through selection for high levels of expression of the COR27 protein.
Technical Abstract: Sodium dodecylsulfate (SDS) polyacrylamide gel electrophoresis (PAGE) and fluorography of in vivo radiolabeled proteins has revealed that protein synthesis in crowns of 'Midiron' and 'Tifgreen' bermudagrass (Cynodon dactylon L. Pers. x C. transvaalensis Burtt-Davy) is altered in association with cold acclimation (CA). Increased synthesis of some proteins in association with CA in Midiron crowns correlates with the greater freezing tolerance of Midiron compared with Tifgreen. This study was undertaken to 1) further characterize alterations in protein synthesis in Midiron and Tifgreen crowns utilizing analytical isoelectric focusing/SDS-PAGE [two-dimensional (2D-) PAGE], and 2) identify cold-regulated (COR) proteins, proteins encoded by genes persistently upregulated during CA, through sequence analysis of peptides recovered after micropreparative 2D-PAGE and protease digestion. Plants were grown for 26 d in controlled-environment chambers under acclimating [8/2 C (day/night) cycle with 10 h photoperiods] or non acclimating [28/24 C] conditions. Proteins synthesized by isolated crowns were in vivo radiolabeled for 16 h with 35S-methionine and 35S-cysteine. Among several groups of COR proteins synthesized in Midiron and Tifgreen crowns, low molecular weight (ca. 20 to 28 kilodalton) basic COR proteins were synthesized in greater amounts and numbers in Midiron and Tifgreen crowns. A prominent 27 kD basic COR protein, designated COR27, from Midiron crowns was identified as a chitinase (E.C. 188.8.131.52) through protein sequencing.